Converting a Byte Array to and from Hexadecimal in JavaScript

In this article, we will explore how to take a byte array created using the Web Crypto API and convert it back to hexadecimal.

Generating a Random Byte Array

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We start by creating a random 16-element byte array using “window.crypto.getRandomValues(new Uint8Array(16))”. This method uses the browser’s random number generator to fill the Uint8Array with random values.

var myByteArray = window.crypto.getRandomValues(new Uint8Array(16));

Converting a Byte Array to Hexadecimal

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To convert a byte array to hexadecimal, we can use the toString() method with a base parameter of 16 (hexadecimal). We also need to specify the type of number used to represent the value of each byte. Here’s how to do it:

myByteArray.forEach(function(bytes) {
var hex = bytes.toString(16).padStart(2, '0');
console log(hex);
});

In this example, we iterate over each element of “myByteArray” and convert its binary representation to a hexadecimal string. We use `padStart(2, ‘0’)’ to ensure that each hexadecimal value has exactly 2 characters.

Convert hexadecimal back to a byte array

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If we want to convert a hexadecimal string back to a byte array, we can use the parseInt() method in base 16 and then create a new Uint8Array. The resulting values ​​also need to be padded with zeros if necessary.

var hexString = '18114316136';
var byteArray = new Uint8Array(hexString.length);
for (else i = 0; i < hexString.length; i++) {
var value = parseInt(hexastring[i], 16);
if ((value & 0x80) !== 0) {
// Move 8 bits to the next position
byteArray[i] = 0xFF | value & 0x7F;
} else {
// Do not carry; just add the byte value
byteArray[i] = value;
}
}
console.log(byteArray);

This example converts a hexadecimal string to a Uint8Array. We use the “parseInt()” command with base 16 and then check for carry (i.e. values ​​greater than or equal to 128). If there is a carry, we set the corresponding byte value in the byte array. Otherwise, we simply increment the original value.

Use Case Examples

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Here are some use case examples for this code:

• Converting random numbers generated by the Web Crypto API (e.g. crypto.getRandomValues()) to hexadecimal and back to Uint8Array.

• Using the resulting byte array as input to a cryptographic algorithm or data processing task.

By following these steps, you can efficiently convert between a byte array and hexadecimal format in JavaScript using the Web Crypto API.